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<meta name="description" content="Customize the pinch-zooming action of GoJS."/> 
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<title>Zoom Pinch GoJS Sample</title>
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    <!-- * * * * * * * * * * * * * -->
    <!-- Start of GoJS sample code -->
    
    <script src="../release/go.js"></script>
    <div class="p-4 w-full">
    <script id="code">
    function init() {

      var $ = go.GraphObject.make;  // for conciseness in defining templates

      myDiagram = $(go.Diagram, "myDiagramDiv",  // create a Diagram for the DIV HTML element
        {
          "undoManager.isEnabled": true  // enable undo & redo
        });

      // define a simple Node template
      myDiagram.nodeTemplate =
        $(go.Node, "Auto",  // the Shape will go around the TextBlock
          $(go.Shape, "RoundedRectangle", { strokeWidth: 0 },
            // Shape.fill is bound to Node.data.color
            new go.Binding("fill", "color")),
          $(go.TextBlock,
            { margin: 8 },  // some room around the text
            // TextBlock.text is bound to Node.data.key
            new go.Binding("text", "key"))
        );

      // Override normal pinch zoom to zoom the selected node instead of the Diagram.

      var originalScale = 1;
      var startDistance = 0; // how far apart the touches are at the start
      var isPinching = false;
      // Initiates pinch-zooming on multi-touch devices.
      myDiagram.toolManager.standardPinchZoomStart = function() {
        var diagram = this.diagram;
        if (diagram === null) return;
        var e = diagram.lastInput;

        var first = e.getMultiTouchViewPoint(0, new go.Point());
        var second = e.getMultiTouchViewPoint(1, new go.Point());
        if (!first.isReal() || !second.isReal()) {
          return;
        }

        // event.isMultiTouch
        // call doCancel to stop the rest of typical toolManager.domousedown/domousemove behavior
        this.doCancel();

        var node = diagram.selection.first();
        if (node === null) return;

        originalScale = node.scale;
        var x = second.x - first.x;
        var y = second.y - first.y;
        var dist = Math.sqrt((x * x) + (y * y));
        startDistance = dist;
        e.bubbles = false;
        e.handled = true;
        isPinching = true;
        myDiagram.startTransaction('zoom node');
      };

      // Continues pinch-zooming (started by {@link #standardPinchZoomStart} on multi-touch devices.
      myDiagram.toolManager.standardPinchZoomMove = function() {
        var diagram = this.diagram;
        if (diagram === null) return;
        var e = diagram.lastInput;

        var first = e.getMultiTouchViewPoint(0, new go.Point());
        var second = e.getMultiTouchViewPoint(1, new go.Point());
        if (!first.isReal() || !second.isReal()) {
          return;
        }

        // event.isMultiTouch
        // call doCancel to stop the rest of typical toolManager.domousedown/domousemove behavior
        this.doCancel();

        var x = second.x - first.x;
        var y = second.y - first.y;
        var dist = Math.sqrt((x * x) + (y * y));
        var scale = dist / startDistance;
        var oldskip = myDiagram.skipsUndoManager;
        var node = diagram.selection.first();
        if (node !== null) node.scale = originalScale * scale;
        e.bubbles = false;
        e.handled = true;
      };

      myDiagram.toolManager.doMouseUp = function() {
        if (isPinching) {
          myDiagram.commitTransaction('zoom node');
          isPinching = false;
        }
        go.ToolManager.prototype.doMouseUp.call(this);
      }

      myDiagram.model = new go.GraphLinksModel(
        [
          { key: "Alpha", color: "lightblue" },
          { key: "Beta", color: "orange" },
          { key: "Gamma", color: "lightgreen" },
          { key: "Delta", color: "pink" }
        ],
        [
          { from: "Alpha", to: "Beta" },
          { from: "Alpha", to: "Gamma" },
          { from: "Beta", to: "Beta" },
          { from: "Gamma", to: "Delta" },
          { from: "Delta", to: "Alpha" }
        ]);
    }

    window.addEventListener('DOMContentLoaded', init);
  </script>

  <div id="sample">
    <!-- The DIV for the Diagram needs an explicit size or else we won't see anything.
       This also adds a border to help see the edges of the viewport. -->
    <div id="myDiagramDiv" style="border: solid 1px black; width:400px; height:400px"></div>
    <p>
      This sample gives an example of customizing
      <a>Tool.standardPinchZoomStart</a> and
      <a>Tool.standardPinchZoomMove</a>.
      Select a node and pinch zoom to see the action modify the scale of the Node instead
      of the scale of the Diagram.
    </p>

  </div>
    </div>
    <!-- * * * * * * * * * * * * * -->
    <!--  End of GoJS sample code  -->
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